Method and apparatus for bone fixation with secondary compression

ABSTRACT

Disclosed is a fracture fixation device, for reducing and compressing fractures in a bone. The fixation device includes an elongate body. An axially moveable proximal anchor is carried by the proximal end of the fixation device and comprises a tubular sleeve that includes a plurality of graduations positioned on an outer surface of the tubular sleeve. The device is rotated into position across the femoral neck and into the femoral head, and the proximal anchor is distally advanced to lock the device into place. In certain embodiments, the elongated body includes a distal anchor with a distal cutting tip.

PRIORITY INFORMATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/991,367, filed Nov. 13, 2001, which is acontinuation-in-part of U.S. patent application Ser. No. 09/822,803,filed Mar. 30, 2001 now U.S. Pat. No. 6,511,481, the entire contents ofwhich are hereby expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to internal bone fracture and fusionfixation devices. In one application, the present invention relates tobone fracture fixation devices and methods adapted for fixation, amongother fractures, of femoral neck and other proximal femoral fractures.

2. Description of the Related Art

The femur, otherwise known as the thigh bone, generally comprises anelongated shaft extending from the hip to the knee. The proximal end ofthe shaft includes a head, a neck, a greater trochanter and a lessertrochanter. The head of the femur fits into the acetabular cup of thehip bone to form a ball and socket joint at the hip. The distal end ofthe femur includes a medial condyle and a lateral condyle. The condylesengage an upper end of the tibia to form the knee joint. Overall, thefemur is the longest and strongest bone in the skeleton. However,portions of the femur are extremely susceptible to fracturing.

Pertrochanteric fractures among geriatric patients are the most frequentin connection with those of the region of the neck of the bone. Theadvanced age and the pathologies which are encountered in these patientsmake a timely stabilization of skeletal injuries necessary in order toreduce to a minimum the bed confinement and the rehabilitation times.Preferably, devices and procedures are utilized which minimizecomplications brought about by the so-called immobilization syndrome,which may be lethal for patients in delicate metabolical circumstances.It is also preferable to reduce to a minimum blood losses related tosurgical intervention. At the same time, the syntheses means utilizedmust be stable in order to allow the patient to very timely assume aseated position and, two or three days following the intervention, toreassume an erect posture with progressive bearing of weight.

Internal fixation of femoral fractures in general is one of the mostcommon orthopedic surgical procedures. Fractures of the femur occur inboth the proximal portion of the femur and the distal portion of thefemur. Fractures of the proximal portion of the femur (hip fractures)are generally classified as femoral neck fractures, intertrochantericfractures and subtrochanteric fractures. Fractures of the distal portionof the femur (knee fractures) are referred to as supracondylarfractures. Supracondylar fractures generally extend vertically betweenthe condyles at the lower end of the femur to separate the distalportion of the femur into two main bone fragments. A fracture line maybe further comminuted to create a plurality of smaller bone fragments.Fractures of the femur which extend into the neck of the bone aregenerally more difficult to treat than fractures restricted to the shaftof the femur.

Operative treatment of the fractures requires that the fractures beinternally fixed and possibly compressed. Fractures of the neck, head ortrochanters of the femur have been treated with a variety of compressionscrew assemblies which include generally a compression plate having abarrel member, a lag screw and a compressing screw. The compressionplate is secured to the exterior of the femur and the barrel member isinserted into a predrilled hole in the direction of the femoral head.The lag screw which has a threaded end and a smooth portion is insertedthrough the barrel member so that it extends across the, break and intothe femoral head. The threaded portion engages the femoral head. Thecompressing screw connects the lag screw to the plate. By adjusting thetension of the compressing screw the compression (reduction) of thefracture can be adjusted.

A variety of elongated implants (nail, screw, pin, etc.) have beendeveloped, which are adapted to be positioned along the longitudinalaxis of the femoral neck with a leading (distal) end portion in thefemoral head so as to stabilize a fracture of the femoral neck. Theelongated implant may be implanted by itself or connected to anotherimplant such as a side plate or intramedullary rod. The leading endportion of the implant typically includes means to positively grip thefemoral head bone (external threads, expanding arms, etc.), but theinclusion of such gripping means can introduce several significantproblems. First, implants with sharp edges on the leading end portion,such as the externally threaded implants, exhibit a tendency to migrateproximally towards the hip joint weight bearing surface afterimplantation. This can occur when the proximal cortical bone hasinsufficient integrity to resist distal movement of the screw head. Suchproximal migration under physiological loading, which is also referredto as femoral head cut-out, can lead to significant damage to theadjacent hip joint. Also, the externally threaded implants can generatelarge stress concentrations in the bone during implantation which canlead to stripping of the threads formed in the bone and thus a weakenedgrip. The movable arms of known expanding arm devices are usually freeat one end and attached at the other end to the main body of the leadingend portion of the implant. As a result, all fatigue loading isconcentrated at the attached ends of the arms and undesirably largebending moments are realized at the points of attachment. In addition,conventional threaded implants generally exhibit insufficient holdingpower under tension, such that the threads can be stripped out of thefemoral head either by overtightening during the implantation procedureor during post operative loading by the patient's weight.

Thus, notwithstanding the variety of efforts in the prior art, thereremains a need for an orthopedic fixation device with improved lockingforce such as within the femoral head in a femoral neck application,which resists migration and rotation, and which can be easily andrapidly deployed within the bone.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the presentinvention, a method of securing a first bone fragment to a second bonefragment. The method comprises the steps of drilling a bore through thefirst bone fragment in the direction of the second bone fragment, andadvancing through the bore a fixation device comprising a first portionand a second portion that are coupled to each other. A distal anchor ofthe fixation device is rotated to secure the fixation device to thesecond fragment, and the proximal anchor is axially advanced to engagethe first fragment.

In one application of the method, the second bone fragment comprises thehead of a femur. Alternatively, the second bone fragment comprises atibia, a fibula, a femur, a humurus, a radius, or an ulna. The firstbone fragment may comprise a condyle.

The method may additionally comprise the step of uncoupling the firstportion from the second portion.

In accordance with another aspect of the present invention, there isprovided a femoral neck fracture fixation device. The device comprisesan elongated body, having a proximal end and a distal end. A helicaldistal anchor is provided on the distal end. In some embodiments, thedistal anchor includes a cutting tip. A first retention structure isprovided on the body, proximal to the distal anchor, and a proximalanchor surface is moveably carried by the body. The proximal anchorincludes a tubular sleeve that in some embodiments includes a pluralityof graduations positioned on an outer surface of the tubular sleeve. Theproximal anchor surface is moveable in the distal direction with respectto the body. The retention structure resists proximal movement of theproximal anchor surface with respect to the body.

In one embodiment, the first retention structure comprises a series ofridges or grooves. A second retention structure is preferably providedon the interior of the tubular sleeve for cooperating with the firstretention structure on the body.

In accordance with another aspect of the present invention, there isprovided a method of treating a femoral fracture. The method comprisesthe steps of drilling at least one and preferably two or three boresdistally into the femur in the direction of a fracture, and advancinginto each bore a fixation device that comprises a body having a firstportion that forms a distal bone anchor and a second portion that formsa proximal end. A proximal component is rotated to engage the distalanchor with the bone distal to the fracture, and a proximal anchor isadvanced distally along the fixation device to compress the fracture.

Preferably, the drilling step comprises drilling the bore along an axiswhich extends through the femoral neck and in the direction of the headof the femur. In one embodiment, the advancing a proximal anchor stepcomprises axially advancing the proximal anchor without rotating theproximal anchor with respect to the fixation device. The femoralfracture may be a capital fracture, subcapital fracture, femoral neckfracture, an intertrochanteric fracture or a subtrochanteric fracture.

Further features and advantages of the present invention will becomeapparent to those of skill in the art in view of the detaileddescription of preferred embodiments which follows, when consideredtogether with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a posterior elevational posterior cross section through theproximal portion of the femur, illustrating two femoral neck fracturefixation devices positioned therein.

FIG. 2 is a side perspective view of a fixation device similar to thatof FIG. 1.

FIG. 3 is a side elevational view of the fixation device of FIG. 2.

FIG. 4 is a cross-sectional view taken through line 4—4 of FIG. 3.

FIG. 4A is an enlarged view of portion 4A of FIG. 4.

FIG. 4B is an enlarged view of portion 4B of FIG. 4 with the fixationdevice in a first position.

FIG. 4C is an enlarged view of portion 4C of FIG. 4 with the fixationdevice in a second position.

FIG. 5 is a cross-sectional view taken through line 5—5 of FIG. 3.

FIGS. 6A-C illustrate a procedure for using of the fixation device ofFIG. 1 to secure a femoral neck fracture.

FIG. 7 is an anterior view of the distal tibia and fibula, with fixationdevices similar to that of FIG. 1 arranged across lateral and medialmalleolar fractures.

FIG. 8 is a side perspective view of a modified fixation device.

FIG. 8A is an enlarged view of portion 8A of FIG. 8.

FIG. 8B is a side view of portion of the fixation device illustrated inFIG. 8A.

FIG. 9 is a front view of the fixation device of FIG. 8 taken in thedirection of arrow A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the fixation devices of the present invention will be disclosedprimarily in the context of fractures of the proximal femur, the methodsand structures disclosed herein are intended for application in any of awide variety of bones and fractures, as will be apparent to those ofskill in the art in view of the disclosure herein. For example, the bonefixation device of the present invention is applicable in a wide varietyof fractures and osteotomies in the hand, such as interphalangeal andmetacarpophalangeal arthrodesis, transverse phalangeal and metacarpalfracture fixation, spiral phalangeal and metacarpal fracture fixation,oblique phalangeal and metacarpal fracture fixation, intercondylarphalangeal and metacarpal fracture fixation, phalangeal and metacarpalosteotomy fixation as well as others known in the art. A wide variety ofphalangeal and metatarsal osteotomies and fractures of the foot may alsobe stabilized using the bone fixation device of the present invention.These include, among others, distal metaphyseal osteotomies such asthose described by Austin and Reverdin-Laird, base wedge osteotomies,oblique diaphyseal, digital arthrodesis as well as a wide variety ofothers that will be known to those of skill in the art. The bonefixation device may be used with or without plate(s) or washer(s), allof which can be either permanent, absorbable, or combinations.

Fractures of the fibular and tibial malleoli, pilon fractures and otherfractures of the bones of the leg may be fixated and stabilized with thepresent invention with or without the use of plates, both absorbable ornon-absorbing types, and with alternate embodiments of the currentinvention. The device may also be used for also be used for anklefusions, fixating and stabilizing fractures and osteotomies of the midand hind foot, Lisfranc fractures, triple arthrodesis, tarsalarthrodesis and osteotomy, or others as are known to those with skill inthe art. One example is the fixation of the medial malleolar avulsionfragment.

The fixation device of the present invention may also be used to attachtissue or structure to the bone, such as in ligament reattachment andother soft tissue attachment procedures. Plates and washers, with orwithout tissue spikes for soft tissue attachment, and other implants mayalso be attached to bone, using either resorbable or nonresorbablefixation devices depending upon the implant and procedure. The fixationdevice may also be used to attach sutures to the bone, such as in any ofa variety of tissue suspension procedures.

For example, peripheral applications for the fixation devices includeutilization of the device for fastening soft tissue such as capsule,tendon or ligament to bone. It may also be used to attach a syntheticmaterial such as marlex mesh, to bone or allograft material such astensor fascia lata, to bone. In the process of doing so, retention ofthe material to bone may be accomplished with the collar as shown, orthe pin and or collar may be modified to accept a suture or othermaterial for facilitation of this attachment.

Specific examples include attachment of the posterior tibial tendon tothe navicular bone in the Kidner operation. This application may beaccomplished, using an appropriately sized implant of the presentinvention along with a washer with distally extending soft tissuespikes. Navicular-cuneiform arthrodesis may be performed utilizing thedevice and concurrent attachment of the tendon may be accomplished.Attachment of the tendon may be accomplished in the absence ofarthrodesis by altering the placement of the implant in the adjacentbone.

Ligament or capsule reattachment after rupture, avulsion or detachment,such as in the ankle, shoulder or knee can also be accomplished usingthe devices disclosed herein.

The fixation devices may be used in combination with semi tubular,one-third tubular and dynamic compression plates, both of metallic andabsorbable composition, if the collar is modified to match the openingon the plate.

The cannulated design disclosed below can be fashioned to accept anantibiotic impregnated rod for the slow adsorption of medicationlocally. This may be beneficial for prophylaxis, especially in openwounds, or when osteomyelitis is present and stabilization of fracturefragments is indicated.

A kit may be assembled for field use by military or sport medical orparamedical personnel. This kit contains an implanting tool, and avariety of implant device size and types. The kit may include additionalcomponents such as sterilization or disinfectant materials, a skinstapler, bandages, gloves, and basic tools for emergent wound andfracture treatment. Antibiotic rods may be included for woundprophylaxis during transport.

Referring to FIG. 1, there is illustrated a posterior side elevationalview of the proximal portion of a femur 10, having a fixation device 12positioned therein. The proximal end of the femur 10 comprises a head 14connected by way of a neck 16 to the long body or shaft 17 of the femur10. As illustrated in FIG. 1, the neck 16 is smaller in diameter thanthe head 14. The neck 16 and head 14 also lie on an axis which, onaverage in humans, crosses the longitudinal axis of the body 17 of thefemur 10 at an angle of about 126°. The risk of fracture at the neck 16is thus elevated, among other things, by the angular departure of theneck 16 from the longitudinal axis of the body 17 of femur 10 and alsothe reduced diameter of the neck 16 with respect to the head 14.

The greater trochanter 18 extends outwardly above the junction of theneck 16 and the body 17 of the femur 10. On the medial side of thegreater trochanter 18 is the trochanteric fossa 20. This depressionaccommodates the insertion of the obturator externus muscle. The lessertrochanter 21 is located posteromedially at the junction of the neck 16and the body 17 of the femur 10. Both the greater trochanter 18 and thelesser trochanter 21 serve for the attachment of muscles. On theposterior surface of the femur 10 at about the same axial level as thelesser trochanter 21 is the gluteal tuberosity 22, for the insertion ofthe gluteus maximus muscle. Additional details of the femur are wellunderstood in the art and not discussed in further detail herein.

FIG. 1 illustrates a fracture 24 which crosses the femur approximatelyin the area of the greater trochanter 18. Fractures of the proximalportion of the femur 10 are generally classified as capital orsubcapital fractures, femoral neck fractures, intertrochantericfractures and subtrochanteric fractures. All of these fractures will bedeemed femoral neck fractures for the purpose of describing the presentinvention.

Referring to FIGS. 1-4, the fixation device 12 comprises a body 28extending between a proximal end 30 and a distal end 32. The length,diameter and construction materials of the body 28 can be varied,depending upon the intended clinical application. In embodimentsoptimized for various fractures in an adult human population, the body28 will generally be within the range of from about 10 mm to about 150mm in length after sizing, and within the range of from about 2 mm toabout 8 mm in maximum diameter. The major diameter of the helicalanchor, discussed below, may be within the range of from about 2.7 mm toabout 12 mm. In general, the appropriate dimensions of the body 28 willvary, depending upon the specific fracture. In rough terms, for amalleolar fracture, shaft diameters in the range of from about 3 mm toabout 4.5 mm may be used, and lengths within the range of from about 25mm to about 70 mm. For condylar fractures, shaft diameters within therange of from about 3.5 mm to about 6.5 mm may be used with lengthswithin the range of from about 25 mm to about 70 mm. For collesfractures (distal radius and ulna), diameters within the range of fromabout 2.0 mm to about 4.5 mm may be used with any of a variety oflengths within the range of from about 6 mm to about 70 mm.

In one embodiment, the body 28 comprises titanium. However, as will bedescribed in more detail below, other metals or bioabsorbable ornonabsorbable polymeric materials may be utilized, depending upon thedimensions and desired structural integrity of the finished fixationdevice 12.

The distal end 32 of the body 28 is provided with a cancellous boneanchor or distal cortical bone anchor 34. Additional details of thedistal bone anchor are described below. In general, in a femoral neckapplication, distal bone anchor 34 is adapted to be rotationallyinserted into the cancellous bone within the head 14 of the femur 10, toretain the fixation device 12 within the femoral head.

Referring to FIGS. 3, 4, and 4A, the body 28 comprises a first portion36 and a second portion 38 that are coupled together at a junction 40.In the illustrated embodiment, the first portion 36 carries the distalanchor 34 while the second portion 38 forms the proximal end 30 of thebody 28. The first and second portions 36, 38 are preferably detachablycoupled to each other at the junction 40. In the illustrated embodiment,the first and second portions 36, 38 are detachably coupled to eachother via interlocking threads. Specifically, as best seen in FIG. 4A,the body 28 includes an inner surface 41, which defines a central lumen42 that preferably extends from the proximal end 30 to the distal end 32throughout the body 28. At the proximal end of the first portion 36, theinner surface 41 includes a first threaded portion 44. The firstthreaded portion 44 is configured to mate with a second threaded portion46, which is located on the outer surface 45 of the second portion 38.The interlocking annular threads of the first and second threadedportions 44, 46 allow the first and second portions 36, 38 to bedetachably coupled to each other. In one modified embodiment, theorientation of the first and second threaded portions 44, 46 can bereversed. That is, the first threaded portion 44 can be located on theouter surface of the first portion 36 and the second threaded portion 46can be located on the inner surface 41 at the distal end of the secondportion 38. Any of a variety of other releasable complementaryengagement structures may also be used, to allow removal of secondportion 38 following implantation, as is discussed below.

In a modified arrangement, the second portion 38 can comprise any of avariety of tensioning elements for permitting proximal tension to beplaced on the distal anchor 34 while the proximal anchor is advanceddistally to compress the fracture. For example, any of a variety oftubes or wires can be removably attached to the first portion 36 andextend proximally to the proximal handpiece. In one such arrangement,the first portion 36 can include a releasable connector in the form of alatching element, such as an eye or hook. The second portion 38 caninclude a complementary releasable connector (e.g., a complementaryhook) for engaging the first portion 36. In this manner, the secondportion 38 can be detachably coupled to the first portion 36 suchproximal traction can be applied to the first portion 36 through thesecond portion as will be explained below. Alternatively, the secondportion 48 may be provided with an eye or hook, or transverse bar,around which or through which a suture or wire may be advanced, bothends of which are retained at the proximal end of the device. Followingproximal tension on the tensioning element during the compression step,one end of the suture or wire is released, and the other end may bepulled free of the device. Alternate releasable proximal tensioningstructures may be devised by those of skill in the art in view of thedisclosure herein.

The proximal end 30 of the fixation device is provided with a proximalanchor 50. Proximal anchor 50 is axially distally moveable along thebody 28, to permit compression of the fracture 24 as will be apparentfrom FIG. 1 and the description below. As will be explained below,complimentary locking structures such as threads or ratchet likestructures between the proximal anchor 50 and the body 28 resistproximal movement of the anchor 50 with respect to the body 28 undernormal use conditions. The proximal anchor 50 preferably can be axiallyadvanced along the body 28 without rotation as will be apparent from thedisclosure herein.

In the illustrated embodiment, proximal anchor 50 comprises a housing 52such as a tubular body, for coaxial movement along the body 28. As bestseen in FIGS. 1 and 4, in a final position, the housing 52 extendsdistally past the junction 40 between the first portion 36 and thesecond portion 38. The housing 52 is provided with one or more surfacestructures 54 such as a radially inwardly projecting flange 56 (seeFIGS. 4B and 4C), for cooperating with complementary surface structures58 on the first portion 36 of the body 28. In the illustratedembodiment, the complimentary surface structures 58 comprise a series ofannular ridges or grooves 60. The surface structures 54 andcomplementary surface structures 58 permit distal axial travel of theproximal anchor 50 with respect to the body 28, but resist proximaltravel of the proximal anchor 50 with respect to the body 28.

For example, as best seen in FIG. 4B, the proximal end of the flange 56is biased towards the longitudinal axis of the body 28. As such, whenthe proximal anchor 50 is urged proximally with respect to the body 28,the flange 56 engages the grooves or ridges 60 of the complementarysurface structures 58. This prevents proximal movement of the proximalanchor 50 with respect to the body 28. In contrast, as best seen in FIG.4C, when the proximal anchor 50 is moved distally with respect to thebody 28, the flange 56 can bend outwardly away from the body 28 and theridges 60 so as to allow the proximal anchor 50 to move distally. Ofcourse, those of skill in the art will recognize that there are avariety of other complementary surface structures, which permit one wayratchet like movement. For example, a plurality of annular rings orhelical threads, ramped ratchet structures and the like for cooperatingwith an opposing ramped structure or pawl can also be used. In oneembodiment, opposing screw threads are dimensioned to function as aratchet.

Retention structures 58 are spaced axially apart along the body 28,between a proximal limit 62 and a distal limit 64. The axial distancebetween proximal limit 62 and distal limit 64 is related to the desiredaxial working range of the proximal anchor 50, and thus the range offunctional sizes of the fixation device 12. Thus, the present inventionprovides a bone fixation device which can provide compression across afracture throughout a range of motion following the placement of thedistal anchor. The distal anchor may be positioned within the cancellousand/or distal cortical bone, and the proximal anchor may be distallyadvanced throughout a range to provide compression across the fracturewithout needing to relocate the distal anchor and without needing toinitially locate the distal anchor in a precise position with respect tothe proximal side of the bone. Providing a working range throughoutwhich tensioning of the proximal anchor is independent from setting thedistal anchor allows a single device to be useful for a wide variety offractures, as well as eliminates the need for accurate devicemeasurement and accurate placement of the distal anchor. In manyapplications, the working range is at least about 10% of the overalllength of the device, and may be as much as 20% or 30% or more of theoverall device length. In the context of a femoral application, workingranges of up to about 10 mm or more may be provided, since estimateswithin that range can normally be readily accomplished within theclinical setting. In other applications, such as a metatarsal fracture,a working range in the area of from about 1 mm to about 2 mm may be allthat is necessary. The embodiments disclosed herein can be scaled tohave a greater or a lesser working range, as will be apparent to thoseof skill in the art in view of the disclosure herein.

The proximal anchor 50 includes a flange 66 that seats against the outersurface of the femur or tissue adjacent the femur. The flange 66 ispreferably an annular flange, to optimize the footprint or contactsurface area between the flange 66 and the femur. Circular or polygonalshaped flanges for use in femoral head fixation will generally have adiameter of at least about 4 mm greater than the adjacent body 28 andoften within the range of from about 4 mm to about 20 mm or more greaterthan the adjacent body 28.

In the illustrated embodiment, the bone contacting surface 68 of theflange 44 is tapered and generally faces the shaft 17 of the femur 10.In other embodiments, the bone contacting surface 69 can resides in orapproximately on a plane, which is perpendicular with respect to thelongitudinal axis of the body 28. In other embodiments, other angularrelationships between the bone contacting surface 68 of the flange 66and the longitudinal axis of the body 28 and housing 52 may be utilized,depending upon the anticipated entrance angle of the body 28 andassociated entrance point surface of the femur 10. In general, thelongitudinal axis extending through the head 14 and neck 16 of the humanfemur is inclined at an angle of approximately 126° from thelongitudinal axis of the long body 17 of the femur 10. Angles betweenthe longitudinal axis of body 28 and tissue contacting surface 68 withinthe range of from about 90° to about 140° will generally be utilized.

In a modified embodiment, the housing 52 of the proximal anchor 50 caninclude one or more one or more barbs that extend radially outwardlyfrom the tubular housing 52. Such barbs provide for self tighteningafter the device has been implanted in the patient as described in aco-pending U.S. patent application Ser. No. 10/012,687 entitled DISTALBONE ANCHORS FOR BONE FIXATION WITH SECONDARY COMPRESSION”, filed Nov.13, 2001, which is hereby expressly incorporated by reference herein.The barbs may be radially symmetrically distributed about thelongitudinal axis of the housing 52. Each barb is provided with atransverse engagement surface, for anchoring the proximal anchor 50 inthe bone. The transverse engagement surface may lie on a plane which istransverse to the longitudinal axis of the housing 50 or may be inclinedwith respect to the longitudinal axis of the tubular 50. In eitherarrangement, the transverse engagement surface 43 generally faces thebone contacting surface 68 of the flange 44. As such, the transverseengagement surface inhibits proximal movement of the proximal anchorwith respect to the bone.

The clinician can be provided an array of proximal anchors 50 of varyingangular relationships between the bone contacting surface 68 and thelongitudinal axis of the body 28 and housing 52 (e.g., 90°, 100°, 110°,120°, and 130°). A single body 28 can be associated with the array suchas in a single sterile package. The clinician upon identifying theentrance angle of the body 28 and the associated entrance point surfaceorientation of the femur 10 can choose the anchor 50 from the array withthe best fit angular relationship, for use with the body 28.

With particular reference to FIG. 3, the proximal end 30 of the body 28may be provided with a rotational coupling 70, for allowing the secondportion 38 of the body 28 to be rotationally coupled to a rotationdevice. The proximal end 30 of the body 28 may be desirably rotated toaccomplish one or two discrete functions. In one application of theinvention, the proximal end 30 is rotated to remove the second portion38 of the body 28 following tensioning of the device across a fractureor to anchor an attachment to the bone. Rotation of the rotationalcoupling 70 may also be utilized to rotationally drive the distal anchorinto the bone. Any of a variety of rotation devices may be utilized,such as electric drills or hand tools, which allow the clinician tomanually rotate the proximal end 30 of the body. Thus, the rotationalcoupling 70 may have any of a variety of cross sectional configurations,such as one or more flats or splines.

In one embodiment, the rotational coupling 70 comprises a proximalprojection of the body 28 having an axial recess with a polygonal crosssection, such as a hexagonal cross section. The rotational coupling 70is illustrated as a female component, machined or milled or attached tothe proximal end 30 of the body 28. However, the rotational coupling mayalso be in the form of a male element, such as a hexagonal or othernoncircular cross sectioned projection.

As illustrated, the body 28 is cannulated to accommodate installationover a placement wire as is understood in the art. The cross section ofthe illustrated central cannulation is circular but in other embodimentsmay be non circular, e.g., hexagonal, to accommodate a correspondingmale tool for installation or removal of the second portion 38 of thebody 28 as will be explained below. In other embodiments, the body 28may partially or wholly solid.

In all of the embodiments illustrated herein, the distal anchor 34comprises a helical locking structure 72 for engaging cancellous and/ordistal cortical bone. In the illustrated embodiment, the lockingstructure 72 comprises a flange that is wrapped around the axial lumen.The flange extends through at least one and generally from about two toabout 50 or more full revolutions depending upon the axial length of thedistal anchor and intended application. For most femoral neck fixationdevices, the flange will generally complete from about 2 to about 20revolutions. The helical flange 72 is preferably provided with a pitchand an axial spacing to optimize the retention force within cancellousbone, to optimize compression of the fracture.

The helical flange 72 of the illustrated embodiment has a generallytriangular cross-sectional shape (see FIG. 4). However, it should beappreciated that the helical flange 72 can have any of a variety ofcross sectional shapes, such as rectangular, oval or other as deemeddesirable for a particular application through routine experimentationin view of the disclosure herein. The outer edge of the helical flange72 defines an outer boundary. The ratio of the diameter of the outerboundary to the diameter of the central lumen can be optimized withrespect to the desired retention force within the cancellous bone andgiving due consideration to the structural integrity and strength of thedistal anchor 34. Another aspect of the distal anchor 34 that can beoptimized is the shape of the outer boundary and the central core, whichin the illustrated embodiment are generally cylindrical.

The distal end 32 and/or the outer edges of the helical flange 72 may beatraumatic (e.g., blunt or soft). This inhibits the tendency of thefixation device 12 to migrate anatomically proximally towards the hipjoint bearing surface after implantation (i.e., femoral head cut-out).Distal migration is also inhibited by the dimensions and presence of theproximal anchor 50, which has a larger footprint than conventionalscrews.

A variety of other arrangements for the distal anchor 32 can also beused. For example, the various distal anchors described in U.S. patentapplication Ser. No. 09/822,803, filed Mar. 30, 2001, entitled “METHODAND APPARATUS FOR FIXATION OF PROXIMAL FEMORAL FRACTURES”, andco-pending U.S. patent application Ser. No. 10/012,687 entitled “DISTALBONE ANCHORS FOR BONE FIXATION WITH SECONDARY COMPRESSION”, filed Nov.13, 2001 can be incorporated into the fixation device 12 describedherein. The entire contents these applications are hereby expresslyincorporated by reference. In particular, the distal anchor may comprisea single helical thread surrounding a central core, much as in aconventional screw, which has been cannulated to facilitate placementover a wire. Alternatively, a double helical thread may be utilized,with the distal end of the first thread rotationally offset from thedistal end of the second thread. The use of a double helical thread canenable a greater axial travel for a given degree of rotation and greaterretention force than a corresponding single helical thread. Specificdistal anchor designs can be optimized for the intended use, taking intoaccount desired performance characteristics, the integrity of the distalbone, and whether the distal anchor is intended to engage exclusivelycancellous bone or will also engage cortical bone.

With particular reference to FIGS. 2 and 5, the fixation device mayinclude an antirotation lock between the first portion 36 of the body 28and the proximal collar 50. In the illustrated embodiment, the firstportion 36 includes a pair of flat sides 80, which interact withcorresponding flat structures 82 in the proximal collar 50. One or threeor more axially extending flats may also be used. As such, rotation ofthe proximal collar 50 is transmitted to the first portion 36 and distalanchor 34 of the body 28. Of course, those of skill in the art willrecognize various other types of splines or other interfit structurescan be used to prevent relative rotation of the proximal anchor and thefirst portion 36 of the body 28.

To rotate the proximal collar, the flange 66 is preferably provided witha gripping structure to permit an insertion tool to rotate the flange66. Any of a variety of gripping structures may be provided, such as oneor more slots, flats, bores or the like. In one embodiment, the flange44 is provided with a polygonal, and, in particular, a pentagonal orhexagonal recess 84. See FIG. 4.

In use, the clinician first identifies a patient having a fracture to betreated, such as a femoral neck fracture, which is fixable by aninternal fixation device. The clinician accesses the proximal femur,reduces the fracture if necessary and selects a bone drill and drills ahole 90 (see FIG. 6A) in accordance with conventional techniques.Frequently, the hole 90 has a diameter within the range from about 3 mmto about 8 mm. This diameter may be slightly larger than the diameter ofthe distal anchor 34. The hole 90 preferably extends up to or slightlybeyond the fracture 24.

A fixation device 12 having an axial length and outside diametersuitable for the hole 90 is selected. The distal end 32 of the fixationdevice 12 is advanced distally into the hole 90 until the distal anchor34 reaches the distal end of the hole 90. The proximal anchor 50 may becarried by the fixation device 12 prior to advancing the body 28 intothe hole 90, or may be attached following placement of the body 28within the hole 90. Once the body 28 and proximal anchor 50 are inplace, the clinician may use any of a variety of driving devices, suchas electric drills or hand tools to rotate the proximal anchor 50 andthus cancellous bone anchor 34 into the head of the femur.

Once the anchor 34 is in the desired location, proximal traction isapplied to the proximal end 30 of body 28, such as by conventionalhemostats, pliers or a calibrated loading device, while distal force isapplied to the proximal anchor 50. In this manner, the proximal anchor50 is advanced distally until the anchor 50 fits snugly against theouter surface of the femur or tissue adjacent the femur and the fracture24 is completely reduced as shown in FIG. 6B. Appropriate tensioning ofthe fixation device 12 is accomplished by tactile feedback or throughthe use of a calibration device for applying a predetermined load on theimplantation device. One advantage of the structure of the presentinvention is the ability to adjust compression independently of thesetting of the distal anchor 34.

Following appropriate tensioning of the proximal anchor 50, the secondportion 38 of the body 28 is preferably detached from the first portion36 and removed. See FIG. 6C. In the illustrated embodiment, thisinvolves rotating the second portion 38 with respect to the firstportion via the coupling 70. In connection with many of the fracturesidentified previously herein, a single fixation device 12 may be allthat is clinically indicated. However, two or three or more fixationdevices 12 may be utilized to reduce a single fracture, depending uponthe location and physical requirements of the fractured portion of thebone. For example, in the case of proximal femoral fractures of the typeillustrated herein, typically at least two and preferably three fixationdevices 12 will be implanted to span the femoral neck. The use of threefixation devices 12 desirably provides sufficient compression across thefracture, as well as minimizes the risk of rotation of the head of thefemur around the axis of a single fixation device 12. The proximal endof the fixation devices may be connected together such as through athree-holed plate or rod, or may be independent of each other.

Following removal of the second portion 38 of each body 28, the accesssite may be closed and dressed in accordance with conventional woundclosure techniques.

In a modified arrangement, the second portion 38 may form part of thedriving device, which is used to rotate the proximal anchor 50 and thuscancellous bone anchor 34 into the head of the femur. The second portion38 is used to apply proximal traction so as to compress the fracture.After appropriate tensioning, the second portion 38 can be de-coupledfrom the first portion 36 and removed with the driving device.

In the foregoing variation, the second portion 38 may be connected to arotatable control such as a thumb wheel on the deployment device. Acontainer may be opened at the clinical site exposing the proximal endof the implant, such that the distal end of the second portion 38 may beremovably coupled thereto. Proximal retraction of the hand tool willpull the implant out of its packaging. The implant may then bepositioned within the aperture in the bone, rotated to set the distalanchor, and the hand piece may be manipulated to place proximal tractionon the second portion 38 while simultaneously distally advancing theproximal anchor. Following appropriate tensioning across the fracture,the second portion 38 may be disengaged from the implant, and removedfrom the patient. In the example of a threaded engagement, the secondportion 38 may be disengaged from the implant by rotating a thumb wheelor other rotational control on the hand piece. In an alternateembodiment, such as where the second portion 38 comprises a pull wire,following appropriate tensioning across the fracture, a first end of thepull wire is released such that the pull wire may be removed from theimplant by proximal retraction of the second end which may be attachedto the hand piece.

Preferably, the clinician will have access to an array of fixationdevices 12, having, for example, different diameters, axial lengths and,if applicable, angular relationships. These may be packaged one perpackage in sterile envelopes or peelable pouches, or in dispensingcartridges which may each hold a plurality of devices 12. Uponencountering a fracture for which the use of a fixation device is deemedappropriate, the clinician will assess the dimensions and loadrequirements, and select a fixation device from the array, which meetsthe desired specifications.

In some instances, a clinician may want to introduce two or morefixation devices 12 into the femoral head 14 to secure the fracture 24.This may be desirable if the clinician determines that, based upon thenature of the fracture 24, there is a possibility that the head 14 ofthe femur 10 could rotate about a single fixation device 12. Even minorrotation can inhibit the healing of the fracture. Significant rotationcan result in failure of the fixation device or necrosis of the femoralhead. Two or more fixation devices 12 may also be desirable where thedirection of the fracture is generally parallel to the axis ofimplantation as is understood in the art.

The fixation device 12 of the present invention may also be used incombination with intramedullary nails or rods, as will be understood bythose of skill in the art.

The fixation device 12 of the present invention may be used in any of awide variety of anatomical settings beside the proximal femur, as hasbeen discussed. For example, lateral and medial malleolar fractures canbe readily fixed using the device of the present invention. Referring toFIG. 7, there is illustrated an anterior view of the distal fibula 120and tibia 122. The fibula 120 terminates distally in the lateralmalleolus 124, and the tibia 122 terminates distally in the medialmalleolus 126.

A fixation device 12 in accordance with the present invention isillustrated in FIG. 7 as extending through the lateral malleolus 124across the lateral malleolar fracture 128 and into the fibula 120.Fixation device 12 includes a distal anchor 34 for fixation within thefibula 120, an elongate body 28 and a proximal anchor 50 as has beendiscussed.

FIG. 7 also illustrates a fixation device 12 extending through themedial malleolus 126, across a medial malleolar fracture 130, and intothe tibia 122. Although FIG. 7 illustrates fixation of both a lateralmalleolar fracture 128 and medial malleolar fracture 130, eitherfracture can occur without the other as is well understood in the art.Installation of the fixation devices across malleolar fractures isaccomplished utilizing the same basic steps discussed above inconnection with the fixation of femoral neck fractures.

FIGS. 8, 8A, 8B, and 9 illustrate a modified fixation device 132 thathas certain modifications that can be used on any of the embodimentsdiscussed herein. With initial reference to FIG. 8, the proximal anchor50 includes a plurality of graduations 134 that are positioned on thehousing 52. The graduations 134 are visual indicia that are spaced,preferably uniformly, along the longitudinal axis of the proximal anchor50. Preferably, the graduations 134 are arranged so that they arevisible from several orientations of the fixation device 132. In theillustrated embodiment, the graduations extend 360 degrees around theproximal anchor 50 and include one or more gaps 136. The graduations 134can be formed by a variety of manufacturing methods, e.g., laseretching, chemical etching, and application of bio-compatible paint.

In use, the graduations 134 facilitate the accurate positioning of thefixation device 132. For example, in one embodiment, the clinicianinserts an elongated member (e.g., a k-wire) of a known length acrossthe fracture 24 or fusion site. The clinician uses a measuring device,which is preferably calibrated to the length of the elongated member, tomeasure the length of the proximal portion of the elongated member so asto determine the length of the device required to fix the fracture orjoint. In a modified embodiment, the elongated member includesmeasurement graduations to directly indicate the desired length of thefixation device or a measuring device can be placed directly across thefracture or fusion site. In another modified embodiment, the elongatedmember can be inserted into a blind hole that has been predrilled to thedesired depth of the fixation device.

With the measurement, the clinician can chose an appropriately sizedfixation device. By comparing the elongated member to the fixationdevice, the clinician can note the graduation 134 that most closelycorresponds to the desired depth of the fixation device. Using thegraduations 134 as a reference, the clinician positions the fixationdevice 132 at the proper depth. In this manner, when proximal tractionis applied to the fixation device and the distal anchor 50 is moveddistally, the distal end 32 of the device will not advance.

The graduations 134, therefore, facilitate accurate positioning of thedistal end 32 of the fixation device 132. Accurate positioning preventsthe distal tip of the fixation device from contacting the distal cortexor penetrating the head of the femur thereby reducing the chances offemoral head cutout, which is common in prior art bone screws. Use ofthe graduations 134 also reduces the amount of fluoroscopy time that isrequired to ensure accurate position of the fixation device.

In the illustrated embodiment, the distal anchor 34 of the fixationdevice 132 forms a double helix comprising two elongated structures 140,142 that are spirally wrapped about a central core 144, which, in turn,defines an central lumen 146 (see FIG. 9). The elongated structures 140,142, are preferably spirally wrapped about the central core from about 2to about 20 or more revolutions. As with the embodiments describedabove, the shape, the width, and height of the elongated bodies 140, 142can be optimized through routine experimentation to optimize theretention force in the bone.

Advantageously, the distal anchor 34 may include a distal cutting tip148. The distal cutting tip 148 is preferably configured such that thedistal anchor 34 is self-drilling and self taping. In the illustratedembodiment, the cutting tip 148 comprises two cutting members 150 a, 150b, which are positioned on the distal end of the elongated members 140,142. The illustrated cutting members 150 a, 150 b include a firstcutting face 152 that defines a plurality of cutting edges as will bedescribed in more detail below. In the illustrated embodiment, the firstcutting face 152 lies generally along a centerline 154 (see FIG. 9) thatextends through the longitudinal axis of the fixation device. As such,the cutting members 150 a, 150 b have a neutral cutting angle. However,in one modified embodiment, the cutting face 152 may have a positiverake to produce a more aggressive cut and a looser path in the bone. Inanother embodiment, the cutting face 152 may have a negative rake angleto produce less aggressive cutting and a tighter cutting path.

As best seen in FIG. 8A, the illustrated cutting tip 148 also includes asecond cutting face 153, which cuts through the central core 144 andextends from the first cutting face 152 of the first cutting member 150a to the first cutting face 152 of the second cutting member 150 b. Thefirst cutting face 152 defines at least a first cutting edge 156 and asecond cutting edge 158. The first and second cutting edges 156, 158extend generally parallel to the longitudinal axis of the fixationdevice 132. The first cutting edge 156 extends generally along theoutside diameter of the axial lumen 146 while the second cutting edge158 extends generally along the outside diameter of the central core144.

A third cutting edge 160 is formed by the intersection of an upper flankof the elongated member 140 with the cutting face 152. In a similarmanner, a fourth cutting edge 162 is formed by the intersection of alower flank of the elongated member 140 with the cutting face 152.Finally, a fifth cutting edge 164 is defined by the intersection of thefirst cutting face 152 with the second cutting face 153. The secondcutting face 153 also defines a cutting edge 166 that generally followsthe outside diameter of the central core 144. All of the cutting edgesare preferably sharpened to provide a smooth, clean, positive cuttingsurface. Such a cutting surface reduces mechanical stresses and theproduction of heat as the fixation device 132 is inserted into the bone.By reducing mechanical stresses, the device 132 is more easily insertedinto the bone. By reducing the production of heat, the cutting surfacehelps to prevent thermal necrosis.

The cutting tip 148 described above has several advantages. For example,the cutting tip 148 cuts a threaded path for the distal anchor 34 asopposed to “rolling” a thread path as is typical in prior art devices.Thread “rolling” produces a threaded path by compressing the bone toconform to the thread of the distal anchor 34. In contrast, threadcutting forms the threaded path by directly cutting the bone tissue.Thread cutting, therefore, tends to generate less heat and lessmechanical stresses than thread rolling. Additionally, because thecutting tip 148 is positioned at the distal end of the elongated members140, 142, the useful threaded length of the fixation device 132 isincreased without increasing the length of the fixation device 132.

It should be appreciated that certain features of the cutting tip 148can also be used with other types distal anchors 34, such as, forexample, a distal anchor with a single or triple helical arrangement orthe distal anchors described in U.S. patent application Ser. No.09/822,803, filed Mar. 30, 2001, and co-pending U.S. patent applicationentitled “DISTAL BONE ANCHORS FOR BONE FIXATION WITH SECONDARYCOMPRESSION”, filed Nov. 13, 2001.

The fixation devices described above may be made from eitherconventional bioabsorbable materials or conventional non-absorbablematerials, combinations thereof and equivalents thereof. In addition,natural materials such as allografts may be used. Examples of absorbablematerials include homopolymers and copolymers of lactide, glycolide,trimethylene carbonate, caprolactone, and p-dioxanone and blendsthereof. The following two blends may be useful: 1) the blend ofpoly(p-dioxanone) and a lactide/glycolide copolymer, as disclosed inU.S. Pat. No. 4,646,741 which is incorporated by reference and (2) theglycolide-rich blend of two or more polymers, one polymer being a highlactide content polymer, and the other being a high glycolide contentdisclosed in U.S. Pat. No. 4,889,119 which is incorporated by reference.Additional bioabsorbable materials are disclosed in copendingapplication Ser. No. 09/558,057 filed Apr. 26, 2000, the disclosure ofwhich is incorporated in its entirety herein by reference.

The fixation devices may also be made from conventional non-absorbable,biocompatible materials including stainless steel, titanium, alloysthereof, polymers, composites and the like and equivalents thereof. Inone embodiment, the distal anchor comprises a metal helix, while thebody and the proximal anchor comprise a bioabsorbable material.Alternatively, the distal anchor comprises a bioabsorbable material, andthe body and proximal anchor comprise either a bioabsorbable material ora non-absorbable material. As a further alternative, each of the distalanchor and the body comprise a non-absorbable material, connected by anabsorbable link. This may be accomplished by providing a concentric fitbetween the distal anchor and the body, with a transverse absorbable pinextending therethrough. This embodiment will enable removal of the bodyfollowing dissipation of the pin, while leaving the distal anchor withinthe bone.

The components of the invention (or a bioabsorbable polymeric coatinglayer on part or all of the anchor surface), may contain one or morebioactive substances, such as antibiotics, chemotherapeutic substances,angiogenic growth factors, substances for accelerating the healing ofthe wound, growth hormones, antithrombogenic agents, bone growthaccelerators or agents, and the like. Such bioactive implants may bedesirable because they contribute to the healing of the injury inaddition to providing mechanical support.

In addition, the components may be provided with any of a variety ofstructural modifications to accomplish various objectives, such asosteoincorporation, or more rapid or uniform absorption into the body.For example, osteoincorporation may be enhanced by providing amicropitted or otherwise textured surface on the components.Alternatively, capillary pathways may be provided throughout the bodyand collar, such as by manufacturing the anchor and body from an opencell foam material, which produces tortuous pathways through the device.This construction increases the surface area of the device which isexposed to body fluids, thereby generally increasing the absorptionrate. Capillary pathways may alternatively be provided by laser drillingor other technique, which will be understood by those of skill in theart in view of the disclosure herein. In general, the extent to whichthe anchor can be permeated by capillary pathways or open cell foampassageways may be determined by balancing the desired structuralintegrity of the device with the desired reabsorption time, taking intoaccount the particular strength and absorption characteristics of thedesired polymer.

One open cell bioabsorbable material is described in U.S. Pat. No.6,005,161 as a poly(hydroxy) acid in the form of an interconnecting,open-cell meshwork which duplicates the architecture of human cancellousbone from the iliac crest and possesses physical property (strength)values in excess of those demonstrated by human (mammalian) iliac crestcancellous bone. The gross structure is said to maintain physicalproperty values at least equal to those of human, iliac crest,cancellous bone for a minimum of 90 days following implantation. Thedisclosure of U.S. Pat. No. 6,005,161 is incorporated by reference inits entirety herein.

The components of the present invention may be sterilized by any of thewell known sterilization techniques, depending on the type of material.Suitable sterilization techniques include heat sterilization, radiationsterilization, such as cobalt 60 irradiation or electron beams, ethyleneoxide sterilization, and the like.

The specific dimensions of any of the bone fixation devices of thepresent invention can be readily varied depending upon the intendedapplication, as will be apparent to those of skill in the art in view ofthe disclosure herein. Moreover, although the present invention has beendescribed in terms of certain preferred embodiments, other embodimentsof the invention including variations in dimensions, configuration andmaterials will be apparent to those of skill in the art in view of thedisclosure herein. In addition, all features discussed in connectionwith any one embodiment herein can be readily adapted for use in otherembodiments herein. The use of different terms or reference numerals forsimilar features in different embodiments does not imply differencesother than those which may be expressly set forth. Accordingly, thepresent invention is intended to be described solely by reference to theappended claims, and not limited to the preferred embodiments disclosedherein.

1. A bone fixation device, comprising: an elongated body, having aproximal end and a distal end; a helical anchor on the distal end of theelongated body; a retention structure on the elongated body that isproximal to the helical anchor; and a proximal anchor, moveably carriedby the body and comprising a tubular sleeve including a plurality ofgraduations positioned on an outer surface of the tubular sleeve;wherein the proximal anchor is movable in the distal direction withrespect to the body, the retention structure resists proximal movementof the proximal anchor with respect to the body; wherein the retentionstructure comprises a series of ridges or grooves.
 2. A bone fixationdevice as in claim 1, wherein the elongated body comprises a firstportion and a second portion that are detachably coupled to each otherat a junction and the proximal anchor, in a first position, extendsdistally past the junction between the first portion and the secondportion.
 3. A bone fixation device as in claim 2, further comprising ananti-rotational structure on the first portion of the elongated body,the anti-rotational structure preventing rotational movement of thefirst portion of the elongated body with respect to the proximal anchor.4. A bone fixation device as in claim 3, further comprising a rotationalcoupling on the second portion of the body.
 5. A bone fixation device asin claim 2, further comprising a first threaded portion on a proximalportion of the first portion and a second threaded portion on a distalportion of the second portion, the first threaded portion and the secondthreaded portion configured to detachably couple the first and secondportions to each other at the junction.
 6. A bone fixation device as inclaim 1, further comprising a gripping structure on the proximal anchor.7. A bone fixation device as in claim 6, wherein the gripping structurecomprises at least one flat side.
 8. A bone fixation device as in claim1, further comprising a second retention structure on the interior ofthe tubular sleeve for cooperating with the first retention structure onthe body.
 9. A bone device as in claim 8, further comprising atransverse flange extending radially outwardly from the tubular sleeve.10. A bone device as in claim 9, wherein the flange is angularlymoveable with respect to a longitudinal axis of the tubular sleeve. 11.A bone fixation device as in claim 1, wherein the proximal anchorincludes a complementary retention structure configured to engage theretention structure on the elongated body to permit axial travel of theproximal anchor with respect to the elongated body in a distal directionbut to resist axial travel of the proximal anchor with respect theelongated body in a proximal direction.
 12. A bone fixation device as inclaim 11, wherein the retention structure on the elongated body has aworking range that is at least about 10 millimeters.
 13. A bone fixationdevice as in claim 11, wherein the retention structure on the elongatedbody has a working range that is at least about 10% of the overalllength of the device.
 14. A bone fixation device as in claim 1, whereinthe device comprises a bioabsorbable material.
 15. A bone fixationdevice as in claim 1, wherein the elongated body is cannulated.
 16. Abone fixation device as in claim 1, wherein the elongated body has adiameter within a range from of about 2 millimeters to about 8millimeters.
 17. A bone fixation device as in claim 1, wherein thedevice has a length within a range of from about 10 millimeters to about150 millimeters.
 18. A bone fixation device as in claim 1, wherein theretention structure on the elongated body has a working range that is atleast about 10 millimeters.
 19. A bone fixation device as in claim 1,wherein the retention structure on the elongated body has a workingrange that is at least about 10% of the overall length of the device.20. A bone fixation device as in claim 1, wherein the helical anchorincludes a distal cutting tip.
 21. A bone fixation device, comprising:an elongated body, having a proximal end and a distal end; a helicalanchor on the distal end of the elongated body; the helical anchorincluding a distal cutting tip; a retention structure on the elongatedbody that is proximal to the helical anchor; and a proximal anchor,moveably carried by the body and comprising a tubular sleeve; whereinthe proximal anchor is movable in the distal direction with respect tothe body, the retention structure resists proximal movement of theproximal anchor with respect to the body, wherein the helical anchorcomprises an elongated member that is spirally wrapped about a centralcore that defines a central lumen.
 22. A bone fixation device as inclaim 21, wherein and the distal cutting tip comprises a cutting facethat cuts across the elongated member and the central core.
 23. A bonefixation device as in claim 22, wherein the cutting face defines atleast a first cutting edge and a second cutting edge, the first cuttingedge extending along the outside diameter of the central lumen while thesecond cutting edge extends generally along the outside diameter of thecentral core.
 24. A bone fixation device as in claim 23, wherein thefirst and second cutting edges are generally parallel to a longitudinalaxis of the fixation device.
 25. A bone fixation device as in claim 23,wherein the cutting face defines a third cutting edge that is formed byan intersection of an upper flank of the elongated member with thecutting face.
 26. A bone fixation device as in claim 25, wherein thecutting face defines a fourth cutting edge that is formed by anintersection of a lower flank of the elongated member.
 27. A bonefixation device as in claim 26, wherein the cutting tip furthercomprises a second cutting face that cuts through the central core anddefines a fifth cutting edge that connects follows the outside diameterof the central core.
 28. A bone fixation device as in claim 21, whereinthe proximal anchor includes a complementary retention structureconfigured to engage the retention structure on the elongated body topermit axial travel of the proximal anchor with respect to the elongatedbody in a distal direction but to resist axial travel of the proximalanchor with respect the elongated body in a proximal direction.
 29. Abone fixation device as in claim 28, wherein the retention structure onthe elongated body has a working range that is at least about 10millimeters.
 30. A bone fixation device as in claim 28, wherein theretention structure on the elongated body has a working range that is atleast about 10% of the overall length of the device.
 31. A bone fixationdevice as in claim 21, wherein the proximal anchor includes a grippingstructure.
 32. A bone fixation device as in claim 31, wherein thegripping structure comprises at least one flat side.
 33. A bone fixationdevice as in claim 21, wherein the device comprises a bioabsorbablematerial.
 34. A bone fixation device as in claim 21, wherein theelongated body is cannulated.
 35. A bone fixation device as in claim 21,wherein the elongated body has a diameter within a range from of about 2millimeters to about 8 millimeters.
 36. A bone fixation device as inclaim 21, wherein the device has a length within a range of from about10 millimeters to about 150 millimeters.
 37. A bone fixation device asin claim 21, wherein the retention structure on the elongated body has aworking range that is at least about 10 millimeters.
 38. A bone fixationdevice as in claim 21, wherein the retention structure on the elongatedbody has a working range that is at least about 10% of the overalllength of the device.
 39. A bone fixation device as in claim 21, whereinthe retention structure on the elongated body comprises a series ofridges or grooves.